1. Field of the Invention
The present invention relates generally to work holders for securing a tool that is being worked upon by a machine or similar such device. More particularly, the present invention is directed to a device for clamping the blade of a shear or similar tool for sharpening by means of a grinding or abrasive wheel. Such clamping devices are normally provided with certain adjustability features to permit the adaptation of the device to the specific structural configuration and required grinding angle of the shear blade being sharpened.
2. Description of the Prior Art
The prior art is replete with various forms of work holders or clamping devices whereby knife blades, sharp tools or shear blades may be secured for sharpening by means of a grinding or abrasive wheel. These devices manifest different forms of clamping arrangements for securing the blade to be sharpened to the general body of the device itself, and also various forms of provisions for adjusting the angular disposition of the blade with respect to the grinding wheel for achieving the optimum grinding angle.
Such prior art devices may generally be classified into two broad groups. First, there are those independent, manually held and guided clamping devices which are not structurally associated or physically integral with the grinding wheel apparatus. Secondly, there are those clamping devices which are integrally or structurally associated with the grinding wheel apparatus such that their manner of use is limited specifically to the configuration and mounting arrangement of the grinding wheels with which they are associated.
The main problems characteristic of work holders or clamping devices for securing a shear or similar blade to be sharpened by a grinding wheel are based primarily upon the manner in which the blade is clamped onto the device and the manner in which the grinding angle of the blade is adjusted with respect to the position of the grinding wheel in accordance with the blade's individual structure. There have been many prior art attempts to provide for a clamping device whereby the blade to be sharpened can be easily and rigidly secured to the device without loosening or twisting of either the blade or clamp mechanism during the grinding operation. In addition, such known clamping devices have also assumed various configurations in attempts to adapt them to a variety of individual blade shapes. These prior art clamping devices, be they independent or structurally associated with a grinding apparatus, normally are only operable with very basic and simple shear blade configurations and do not permit the effective clamping and sharpening of more complex shear blade structures such as those having a serrated or "pinking" edge configuration. Such prior art clamping devices further do not permit a very rigid and secure clamping of the blade with the usual result being that the blade tends to move or twist, thereby destroying the precise grinding angle and position required for proper sharpeneing.
The critical problem of adjusting the precise required angle of the clamped blade with respect to the grinding wheel so that effective sharpening can be achieved is difficult to solve. Heretofore known devices manifest various forms of adjustment structures for achieving the desired grinding angle. However, the majority of these solutions are cumbersome, complex and expensive to produce. These devices are also almost invariably an integral part of the overall grinding apparatus since it has heretofore been difficult if not impossible to provide for an independent, manually operated clamping device which is both simple in structure and capable of precise grinding angle adjustment.